CSC231 GetLocalTime.asm
--D. Thiebaut 22:33, 4 December 2008 (UTC)
This program shows how to get the time of day in year, month, day, hours, minutes, and seconds.
;;; getLocalTime.asm
;;; D. Thiebaut
;;;
;;; Computes the local time in day, month, year, hour, minute,
;;; second values.
;;;
;;; The driver.c program must be modified for this occasion as
;;; follows:
;;;
;;; -----------------------------------------------------------
;;;
;;; #include <stdio.h>
;;; #include <time.h>
;;;
;;; extern int asm_main( void ); // entry point of assembly
;;; extern time_t currentTime; // assembly storage for time
;;;
;;; int* _getLocalTime( ) {
;;; return (int*) localtime( ¤tTime );
;;; }
;;;
;;; int main() {
;;; // call assembly program
;;; asm_main();
;;; }
;;;
;;; -----------------------------------------------------------
;;;
;;; To assemble, link and run:
;;; nasm -f elf asm_io.asm
;;; nasm -f elf xxxx.asm
;;; gcc -o xxxx driver.c asm_io.o xxxx.o
;;;
;;;
%include "asm_io.inc"
extern _getLocalTime ;function in C driver program
global currentTime ;make this available to C program
;; -------------------------
;; data segment
;; -------------------------
section .data
;;; time structure for int 0x80, 78
currentTime equ $
tvsec dd 0 ; number of seconds since midnight
tvusec dd 0 ; number of useconds
;;; time structure for local time
timeinfo equ $
tm_sec dd 0 ;seconds after the minute 0-61*
tm_min dd 0 ;minutes after the hour 0-59
tm_hour dd 0 ;hours since midnight 0-23
tm_mday dd 0 ;day of the month 1-31
tm_mon dd 0 ;months since January 0-11
tm_year dd 0 ;years since 1900
tm_wday dd 0 ;days since Sunday 0-6
tm_yday dd 0 ;days since January 1 0-365
tm_dst dd 0 ;Daylight Saving Time flag
TIMELEN equ ($-timeinfo)/4
;; -------------------------
;; code area
;; -------------------------
section .text
global asm_main
asm_main:
;;; get the local time in year, month, day, hour, min, sec...
call getLocalTime
;;; print a few of the values obtained
mov eax, [tm_mday]
call print_int
call print_nl
mov eax, [tm_mon]
add eax, 1 ;because Jan is 0
call print_int
call print_nl
mov eax, [tm_year]
add eax, 1900 ;because we get an offset since 1900
call print_int
call print_nl
mov eax, [tm_hour]
call print_int
call print_nl
mov eax, [tm_min]
call print_int
call print_nl
mov eax, [tm_sec]
call print_int
call print_nl
;; return to C program
ret
;;; ------------------------------------------------------------------
;;; getTimeOfDay: asks Linux for the # of seconds since Jan 1, 1970.
;;; ------------------------------------------------------------------
getTimeOfDay:
mov eax, 78 ; system call: get time of day
mov ebx, tvsec ; address of buffer for secs/usecs
mov ecx, 0 ; NULL for timezone
int 0x80
ret
;;; ------------------------------------------------------------------
;;; getLocalTime: first gets the time of day, then ask Linux to transform
;;; this information into month, day, hours, minutes, sec.,
;;; etc. The information is stored in the dwords stored at
;;; timeinfo in the data segment.
;;; ------------------------------------------------------------------
getLocalTime:
;;; get the # of sec since Jan 1, 1970
call getTimeOfDay
;;; transform this # of sec into local time
call _getLocalTime ; call the C function
mov esi, eax
mov edi, timeinfo
mov ecx, TIMELEN
copyTime:
mov eax, [esi]
mov [edi],eax
add esi, 4
add edi, 4
loop copyTime
ret
